Donor-acceptor dyads and triads employing core-substituted naphthalene diimides:a synthetic and spectro (electrochemical) study

Donor-acceptor dyads and triads comprising core-substituted naphthalene diimide (NDI) chromophores and either phenothiazine or phenoxazine donors are described. Synthesis combined with electrochemical and spectroelectrochemical investigations facilitates characterisation of the various redox states of these molecules, confirming the ability to combine arrays of electron donating and accepting moieties into single species that retain the redox properties of these individual moieties

Photoinduced radical formation in hydrogen-bonded organic frameworks

Hydrogen-bonded organic frameworks (HOFs) constructed from naphthalene-diimide bearing tectons undergo photochromic changes whilst forming radical bearing species within the framework structure

Biomimics of [FeFe]-hydrogenases with a pendant amine:Diphosphine complexes [Fe₂(CO)₄{µ-S(CH₂)_nS}{κ²-(Ph₂PCH₂)₂NR}] (n = 2, 3; R = Me, Bn) towards H₂ oxidation catalysts

We report the synthesis and molecular structures of [FeFe]-ase biomimics [Fe 2 (CO) 4 {μ-S(CH 2 ) n S}{ κ2 - (Ph 2 PCH 2 ) 2 NR}] ( 1–4 ) ( n = 2, 3; R = Me, Bn) and a comparative study of their protonation and re- dox chemistry, with the aim of assessing their activity as catalysts for H 2 oxidation. They are prepared in good yields upon heating the hexacarbonyls and PCNCP ligands in toluene, a minor product of one reaction ( n = 3, R = Bn) being pentacarbonyl [Fe 2 (CO) 5 (μ-pdt){Ph 2 PCH 2 N(H)Bn}] ( 5 ). Crystal structures show short Fe-Fe bonds (ca. 2.54 ˚A) with the diphosphine occupying basal-apical sites. Each undergoes a quasi-reversible one-electron oxidation and IR-SEC shows that this results in formation of a semi-bridging carbonyl. As has previously been observed, protonation products are solvent dependent, nitrogen being the favoured site of protonation site upon addition of one equivalent of HBF 4 .Et 2 O in d 6 -acetone, while hydride formation is favoured in CD 2 Cl 2 . However, the rate of N to Fe 2 proton-transfer varies greatly with the nature of both the dithiolate-bridge and amine-substituent. Thus with NMe complexes ( 1–2 ) N- protonation is favoured in acetone affording a mixture of endo and exo isomers, while for NBn complexes ( 3–4 ) proton-transfer to afford the corresponding μ-hydride occurs in part (for 3 edt) or exclusively (for 4 pdt). In acetone, addition of a further equivalent of HBF 4 .Et 2 O generally does not lead to hydride for- mation, but in CD 2 Cl 2 dications [Fe 2 (CO) 4 {μ-S(CH 2 ) n S}( μ-H){ κ2 -(Ph 2 PCH 2 ) 2 NHR}] 2 + result, in which the diphosphine can adopt either dibasal or basal-apical positions. Proton-transfer from Fe 2 to N has been previously identified as a required transformation for H 2 oxidation, as has the accessibility of the all- terminal carbonyl isomer of cations [Fe 2 (CO) 4 {μ-S(CH 2 ) n S}{ κ2 -(Ph 2 PCH 2 ) 2 NR}] + . We have carried out a preliminary H 2 oxidation study of 3, oxidation by Fc[BF 4 ] in the presence of excess P(o-tolyl) 3 affording [HP(o-tol) 3 ][BF 4 ], with a turnover of ca. 2.3 ±0.1 mol of H 2 consumed per mole of 3

A chirally-locked bis-perylene diimide macrocycle: consequences for chiral self-assembly and circularly polarized luminescence

Macrocycles containing chiral organic dyes are highly valuable for the development of supramolecular circularly polar-ized luminescent (CPL) materials, where a preorganized chiral framework is conducive to directing π–π self-assembly and delivering a strong and persistent CPL signal. Here, perylene diimides (PDIs) are an excellent choice for the organic dye component because, alongside their tuneable photophysical and self-assembly properties, functionalization of the PDI’s core yields a twisted, chiral π-system, capable of CPL. However, configurationally stable PDI-based macrocycles are rare, and those that are also capable of π–π self-assembly beyond dimers are unprecedented, both of which are advanta-geous for robust self-assembled chiroptical materials. In this work, we report the first bay-connected bis-PDI macrocycle that is configurationally stable (ΔG‡ > 155 kJ mol⁻1). We use this chirally-locked macrocycle to uncover new knowledge of chiral PDI self-assembly and to perform new quantitative CPL imaging of the resulting single crystal materials. As such, we discover that the chirality of a 1,7-disubstituted PDI provides a rational route to designing H-, J- and concomitant H- and J-type self-assembled materials, important arrangements for optimising (chir)optical and charge/energy transport properties. Indeed, we reveal that CPL is amplified in the single crystals of our chiral macrocycle by quantifying the de-gree of emitted light circular polarization from such materials for the first-time using CPL-Laser Scanning Confocal Mi-croscopy

Biomimics of [FeFe]-hydrogenases incorporating redox-active ligands:synthesis, redox properties and spectroelectrochemistry of diiron-dithiolate complexes with ferrocenyl-diphosphines as Fe₄S₄ surrogates

Article prepares and characterizes a small series of new [FeFe]-ase biomimics which contain a ferrocenyl diphosphine as a surrogate for the Fe₄S₄ moiety in the H-cluster of the enzyme. Mechanistic details of both proton reduction and H₂ oxidation have been studied by DFT allowing speculative reaction schemes to be developed

The Pink Box: Exclusive Homochiral Aromatic Stacking in a Bis-perylene Diimide Macrocycle

This work showcases chiral complementarity in aromatic stacking interactions as an effective tool to optimize the chiroptical and electrochemical properties of perylene diimides (PDIs). PDIs are a notable class of robust dye molecules and their rich photo- and electrochemistry and potential chirality make them ideal organic building blocks for chiral optoelectronic materials. By exploiting the new bay connectivity of twisted PDIs, a dynamic bis-PDI macrocycle (the “Pink Box”) is realized in which homochiral PDI–PDI π–π stacking interactions are switched on exclusively. Using a range of experimental and computational techniques, we uncover three important implications of the macrocycle’s chiral complementarity for PDI optoelectronics. First, the homochiral intramolecular π–π interactions anchor the twisted PDI units, yielding enantiomers with half-lives extended over 400-fold, from minutes to days (in solution) or years (in the solid state). Second, homochiral H-type aggregation affords the macrocycle red-shifted circularly polarized luminescence and one of the highest dissymmetry factors of any small organic molecule in solution (glum = 10–2 at 675 nm). Finally, excellent through-space PDI–PDI π-orbital overlap stabilizes PDI reduced states, akin to covalent functionalization with electron-withdrawing groups